JP4232573B2 - Magnetic bearing control device and magnetic levitation device - Google Patents

Description

  The present invention relates to a magnetic bearing control device for a magnetic bearing used in a turbo molecular pump, a machine tool, and the like, and a magnetic levitation device including the magnetic bearing control device.

  Conventionally, magnetic bearings are often adopted as bearings for turbomolecular pumps. In the magnetic bearing type turbo molecular pump, the floating position of the rotor magnetically supported by the electromagnet is constantly monitored by a displacement sensor. In general, a reluctance type sensor using a carrier wave is used as a displacement sensor, and the displacement of the rotor is detected using a change in inductance caused by a gap change (see, for example, Patent Document 1).

  Then, a demodulation process is performed by multiplying the response wave from the displacement sensor by the demodulation sine wave. The demodulated signal is subjected to various filter processes and sensor gain / sensor offset adjustment, and then subjected to PID calculation processing.

  By the way, it is known that the gain / offset changes depending on the relationship between the phase of the response wave at the time of demodulation and the phase of the sine wave to be multiplied. Although the optimum phase is set by design, there may be a phase shift from the optimum phase due to manufacturing variations. In such cases, the phase of the sensor response wave and the phase of the sine wave are adjusted. There was a need to do.

JP 2001-336528 A

  However, the adjustment using the D / A output described above is complicated, and the adjustment itself cannot be performed when the configuration is not such that D / A output can be performed. In addition, since the phase of the sensor response wave changes depending on the rotor position, it is difficult to determine whether or not the phase is appropriate. If the phase adjustment is not performed properly, the magnetic bearing may become uncontrollable.

According to the first aspect of the present invention, a carrier wave signal is applied to a sensor for detecting the floating position of the supported body, a response wave signal from the sensor is multiplied by a demodulating sine wave signal, and demodulation is performed. Applied to a magnetic bearing control device that controls the excitation current of the electromagnet to be supported based on the demodulated signal, a phase shift unit that shifts the phase of the sine wave signal, and the floating position of the supported body at the first position and Multiplication signals that are set in order to the second position, change the phase of the sine wave signal from 0 (deg) to 360 (deg) by the phase shift unit at each setting position, and acquire the signals after multiplication at that time, respectively. Based on the signal acquired by the acquisition means, the multiplication signal acquisition means, the phase calculation means for calculating the phase at which the gain of the demodulated signal is maximized, and the phase calculated by the phase calculation means in the magnetic bearing control phase Characterized by comprising a phase setting means for setting the phase shift amount of the shift unit.
According to the second aspect of the present invention, a carrier wave signal is applied to a sensor that detects the floating position of the supported body, a response wave signal from the sensor is multiplied by a demodulation sine wave signal, and demodulation is performed. Applied to a magnetic bearing control device that controls the excitation current of an electromagnet to be supported on the basis of a demodulated signal, a phase shift unit that shifts the phase of a sine wave signal to generate a carrier wave signal, and a floating position of a supported body Are sequentially set to the first position and the second position, and the phase shift unit changes the phase of the sine wave signal from 0 (deg) to 360 (deg) at each set position, and the signal after multiplication at that time Respectively, a phase calculation means for calculating a phase at which the gain of the demodulated signal is maximized based on the signal acquired by the multiplication signal acquisition means, and a phase calculated by the phase calculation means The magnetic Characterized by comprising a phase setting means for setting the phase shift amount of the phase shift unit in the receiving control.
According to a third aspect of the present invention, in the magnetic bearing control device according to the first or second aspect, the phase calculation means is obtained when the multiplication signal obtained when the first position is set and the second position is set. The phase having the maximum difference from the multiplied signal is calculated as the phase.
According to a fourth aspect of the present invention, in the magnetic bearing control device according to any one of the first to third aspects, the A / D conversion means for converting the response wave signal from the sensor into a digital value is provided, and the digital value is converted. Demodulation is performed by digital arithmetic processing based on the signal.
According to a fifth aspect of the present invention, in the magnetic bearing control device according to any one of the first to fourth aspects, acquisition of a signal after multiplication by the multiplication signal acquisition means and phase calculation each time energization of the magnetic bearing control device is started. A series of operations of calculating the phase by the means and setting the phase shift amount by the phase setting means are performed.
A sixth aspect of the present invention is the magnetic bearing control device according to any one of the first to fifth aspects, wherein the storage unit stores the phase shift amount set by the phase setting means, and the phase shift stored in the storage unit. And an abnormality warning unit that issues a bearing abnormality warning when the phase deviation calculated by the phase calculation unit with respect to the quantity is greater than or equal to a predetermined reference value.
According to the seventh aspect of the present invention, a carrier wave signal is applied to a sensor for detecting the floating position of the supported body, the response wave signal from the sensor is multiplied by a demodulating sine wave signal, and demodulation is performed. Applied to a magnetic bearing control device that controls the excitation current of the electromagnet to be supported based on the demodulated signal, a phase shift unit that shifts the phase of the sine wave signal, and the floating position of the supported body at the first position and Multiplication signals that are set in order to the second position, change the phase of the sine wave signal from 0 (deg) to 360 (deg) by the phase shift unit at each setting position, and acquire the signals after multiplication at that time, respectively. Based on the acquisition unit, the signal acquired by the multiplication signal acquisition unit, the phase calculation unit that calculates the phase at which the gain of the demodulated signal is maximized, and the phase calculation unit each time the magnetic bearing control device is energized Calculated position Deviation for the predetermined criterion, characterized in that a fault warning means for issuing a warning of the bearing abnormality if it is determined that the predetermined value or more by the determination means and determination means for determining whether or not a predetermined value or more.
According to an eighth aspect of the present invention, a magnetic levitation apparatus includes the magnetic bearing control device according to any one of the first to seventh aspects and a magnetic bearing controlled by the magnetic bearing control device.

  According to the present invention, since the gain of the response wave signal is adjusted to be maximized, the S / N ratio of the sensor signal can be improved, and the control stability can be improved.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining a magnetic bearing control device according to the present invention, and is a block diagram of a magnetic levitation control system. In FIG. 1, the upper half of the two-dot chain line shows the schematic configuration of the magnetic bearing 1, and the upper half of the two-dot chain line shows the drive control device 2. The block diagram shown in FIG. 1 relates to one of the five-axis control type magnetic bearings as shown in FIG. 2, for example, and shows the radial bearing 51x.

  The 5-axis magnetic bearing in FIG. 2 includes four sets of radial electromagnets 51x, 51y, 52x, 52y and one set of axial electromagnets 53z for the rotor 4 rotated by the motor 6. Reference numeral 41 denotes a disk provided at one end of the rotor 4, and the axial electromagnet 53 z is provided so as to sandwich the disk 41. Although not shown, a displacement sensor is provided for each electromagnet 51x, 51y, 52x, 52y, 53z.

  Returning to FIG. 1, reference numeral 71x denotes a displacement sensor provided in association with the electromagnet 51x, and a pair of sensors are provided with the rotor 4 being sandwiched in the same manner as the electromagnet 51x. Sensor signals from the respective displacement sensors 71 x are input to the sensor circuit 5. The displacement sensor 71x is an inductance type sensor, and converts the gap displacement into an electrical signal by using a change in sensor unit impedance caused by a gap change with the rotor 4. The sensor facing surface of the rotor 4 is made of a ferromagnetic material or a conductor.

  The drive control device 2 is provided with a sensor circuit 5, a magnetic bearing control unit 3, and an excitation amplifier 8. The magnetic bearing control unit 3 includes an A / D converter 301, a D / A converter 302, a DSP (digital signal processor) 307, and a storage unit 306 having a ROM 304, a RAM 305, and the like. Reference numeral 2 denotes a display device for displaying a bearing state and a warning display described later.

  A carrier wave of several tens of kHz is applied to the radial displacement sensor 71x by the sensor circuit 5, and the carrier wave is amplitude-modulated in accordance with a change in impedance of the sensor section caused by the gap displacement. This response wave (AM wave) is input to the magnetic bearing control unit 3 through the sensor circuit 5 as a sensor signal. In the case of the radial displacement sensor 71x including a pair of displacement sensors, the difference between the response wave signals is calculated in the sensor circuit 5 as will be described later, and the difference component is input to the magnetic bearing control unit 3 as a sensor signal.

  The analog sensor signal input to the magnetic bearing control unit 3 is converted into a digital value by the A / D converter 301 and then input to the DSP 307. A magnetic levitation control constant is input to the storage unit 306 in advance, and the DSP 307 calculates an excitation current to flow through the electromagnet 51x based on the output of the displacement sensor 7 and the control constant.

  For example, when the floating position of the rotor 4 is shifted to the left side from the proper position, control is performed so that the excitation current of the right electromagnet 51x is increased to the proper position. The current control amount at this time is calculated by PID calculation. The DSP 307 outputs a control signal corresponding to the excitation current to be supplied. The control signal is converted into an analog value by the D / A converter 302 and then input to the excitation amplifier 8.

  FIG. 3 is a block diagram showing the configuration of the sensor circuit 5 and the DSP 307 related to the radial electromagnet 51x. The DSP 307 is provided with a sine wave discrete value generation unit 320 that generates a sine wave discrete value. The sine wave discrete value generated by the sine wave discrete value generation unit 320 is converted into an analog wave by the D / A converter 308, and the analog wave is input to the sensor circuit 5. Since this analog wave contains harmonics, it is filtered by a filter circuit 501 such as a low-pass filter or a band-pass filter. The analog wave output from the filter circuit 501 is applied as a carrier wave to each of the displacement sensors 71x connected in series to the resistor R.

  A response wave from each displacement sensor 71 x is input to a difference circuit 502 provided in the sensor circuit 5, and a difference calculation is performed by the difference circuit 502. The differential signal from the differential circuit 502 is amplified by the preamplifier 503, converted into a digital signal by the A / D converter 301, and input to the multiplier 322 of the DSP 307. The multiplication unit 322 receives the sine wave discrete value from the sine wave discrete value generation unit 320 via the phase shift unit 321. The phase shift unit 321 shifts the phase of the sine wave discrete value by the optimum phase shift amount θ 0, and performs phase shift based on the command of the phase adjustment unit 326. The optimum phase shift amount θ0 at this time is stored in the storage unit 306 in advance.

  The multiplier 322 multiplies the response wave signal by a sine wave discrete value to perform demodulation processing. After the harmonic component is removed from the demodulated signal by the low-pass filter 323, the gain / offset adjustment unit 324 adjusts the sensor gain and the sensor offset, and the sensor signal is sent to the PID calculation unit 325. The PID calculation unit 325 calculates the current control amount of the electromagnet 51x (see FIG. 1) by PID calculation, and outputs a control signal based on the calculation result. The control signal is input to the excitation amplifier 8 after being converted into an analog value by the D / A converter 302.

<About phase shift adjustment>
However, as described above, the gain / offset of the sensor signal output from the gain / offset adjustment unit 324 changes according to the mutual phase relationship when the multiplication unit 322 multiplies the response wave signal and the sine wave discrete value. To do. Although the phase shift unit sets the gain / offset to be optimal in design, the phase relationship may actually deviate from the optimal value. In such a case, as described above, it is necessary to adjust the gain / offset to be optimum while taking out the sensor signal and observing it with an oscilloscope or the like.

  In the present embodiment, this phase adjustment is automatically performed by the phase adjustment unit 326. FIG. 4 is a flowchart showing the procedure of the phase shift adjustment process. This phase adjustment process starts when the drive control device 2 is powered on. In step S1, the magnetic bearing 1 is driven and the rotor 4 is magnetically levitated. In step S2, the exciting current of the electromagnet 51x is controlled to move the floating position of the rotor 4 from the center position to the first floating position.

  1 and 2 includes a mechanical bearing (not shown) that supports the rotor 4 when the magnetic bearing 1 is not operating. Therefore, the radial flying position of the rotor 4 is limited by the mechanical bearing. Here, the state in which the rotor 4 is attracted in the direction of the electromagnet 51x on the right side of FIG. 1 and the rotor 4 is in contact with the mechanical bearing is defined as the first floating position.

  Then, in the state where it is levitated to the first ascent position, the phase shift amount by the phase shift unit 321 is changed from 0 (deg) to 360 (deg) by the phase adjustment unit 326, and the phase θ and sensor signal at that time are changed. The θ-sensor signal curve A that is the relationship is obtained. The curve indicated by the symbol A in FIG. 5A is the θ-sensor signal curve A, the vertical axis is the output value (V), and the horizontal axis is the phase θ. This sensor signal is a signal output from the gain / offset adjustment unit 324, and its output value is detected by the phase adjustment unit 326.

  In step S3, the flying position of the rotor 4 is moved from the first flying position to the second flying position. Then, in the state of being levitated to the second ascent position, the phase shift amount by the phase shift unit 321 is changed from 0 (deg) to 360 (deg) by the phase adjustment unit 326, and the phase θ and sensor signal at that time are changed. (Theta) -sensor signal curve B which is the relationship of these is acquired (refer Fig.5 (a)). Here, the state in which the rotor 4 is attracted in the direction of the electromagnet 51x on the left side in FIG. 1 and the rotor 4 is in contact with the mechanical bearing is defined as the second floating position.

  In step S4, subtraction is performed between the data of the same phase of the θ-sensor signal curves A and B, the θ-gain curve C is obtained, and the phase θ1 at which the value is maximum is calculated. FIG. 5B shows the θ-gain curve C, and it can be seen that the maximum value is obtained when θ1 = 0 or 180. FIG. The phase θ1 at which the gain is maximum is the optimum phase shift amount of the sine wave discrete value.

  In step S5, the deviation Δθ (= | θ0−θ1 |) of the optimum phase shift amount θ1 calculated in step S4 with respect to the optimum phase shift amount θ0 stored in the storage unit 306 is equal to or larger than a predetermined reference value Δθ0. It is determined whether or not. If it is determined in step S5 that the difference Δθ is smaller than the reference value Δθ0, the process proceeds to step S6, and the phase θ1 calculated in step S4 is stored as θ0 in the storage unit 306. That is, θ0 is rewritten. Then, based on the rewritten θ 0, a phase shift of the sine wave discrete value by the phase shift unit 321 is performed, and the series of phase adjustment processing ends.

  When the phase adjustment unit 326 is adjusted, the value of the sensor signal input to the gain / offset adjustment unit 329 changes. However, the gain / offset adjustment unit 324 performs gain adjustment and offset adjustment according to changes in the sensor signal. Is done.

  On the other hand, if it is determined in step S5 that Δθ ≧ Δθ0, the process proceeds to step S7 to generate a warning indicating that a bearing abnormality has occurred. For example, a warning display is displayed on the display unit 9 on the drive control device 2. Generally, when there is a deviation from the appropriate phase shift amount, the deviation is from the beginning of manufacture, and once the deviation is corrected, the deviation rarely recurs, if any. . However, when an abnormality occurs in the displacement sensor 71x, for example, when a disconnection occurs, the output value of the gain / offset adjustment unit 324 changes greatly to satisfy the condition of Δθ ≧ Δθ0.

  In the case of a 5-axis control type magnetic bearing as shown in FIG. 2, the phase shift adjustment process as described above is performed for each axis. FIG. 6 is a block diagram showing the configuration of the sensor circuit 5 and the DSP 307 related to the axial electromagnet 53z of FIG. 2, and the sensor circuit 5 is different from FIG. In the case of the axial displacement sensor 73, unlike the radial displacement sensor 51x, the sensor is provided on one of the upper and lower sides of the disk 41 in FIG.

  In the case of FIG. 6, the difference circuit 502 receives a response wave from the axial displacement sensor 73 and a signal having a constant amplitude generated from the carrier wave signal (hereinafter referred to as a carrier wave reference signal). Then, the difference between the response wave and the carrier wave reference signal is calculated as the difference signal. The carrier wave reference signal is formed by gain-correcting the carrier wave from the filter circuit 501 with the gain correction unit 504 and phase-shifting with the phase shift unit 505. This is because when the difference circuit 502 calculates the difference, if there is a phase shift between the signals, the S / N ratio is deteriorated. Therefore, the phase shift by the phase shift unit 505 causes the phase shift to be almost zero. It is trying to become.

  In the example described above, the phase shift adjustment process is automatically performed every time power is supplied. However, the drive control device 2 is provided with a phase shift adjustment instruction switch so that the phase shift adjustment is performed according to an instruction from the operator. May be. Further, when the phase shift adjustment process is performed at the time of manufacture and shipment, the drive control device 2 may be adjusted using a dummy instead of the regular magnetic bearing 1. As a result, the S / N ratio of the sensor signal is improved, and the control stability of the magnetic bearing can be improved.

[Modification 1]
FIG. 7 is a diagram showing a modification of the circuit shown in FIG. In the example shown in FIG. 3, the demodulated sine wave discrete value input to the multiplier 322 is phase-shifted, but in FIG. 7, the sine wave discrete value for generating the carrier wave applied to the radial displacement sensor 71x is phase-shifted. The phase is shifted by the shift unit 321. When the phase of the carrier wave is shifted, the response wave from the radial displacement sensor 71x is also phase-shifted. As a result, the phase relationship between the differential signal input to the multiplier 322 and the sine wave discrete value is changed. Can do. The phase shift adjustment method is the same as in FIG.

[Modification 2]
FIG. 8 is a diagram showing another modification. In the example shown in FIG. 3, the sine wave generated by the DSP 307 is used as the carrier wave. However, in the example shown in FIG. 8, the carrier wave generation unit 505 provided in the sensor circuit 5 generates and applies the carrier wave.

  In the correspondence between the embodiment described above and the elements of the claims, the rotor 4 is a supported body, the phase adjustment unit 326 is a multiplication signal acquisition unit, a phase calculation unit, a phase setting unit, and a determination unit, and a display unit. Reference numerals 9 respectively constitute abnormality warning means. In addition, the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired.

It is a block diagram which shows the basic composition of the magnetic levitation control system of a magnetic bearing apparatus. It is a conceptual diagram of a 5-axis control type magnetic bearing. 2 is a block diagram illustrating configurations of a sensor circuit 5 and a DSP 307. FIG. It is a flowchart which shows the procedure of a start shift adjustment process. It is a figure explaining a phase adjustment process, (a) shows theta-sensor signal curve A and B, (b) shows theta-gain curve C. It is a block diagram which shows the structure of the sensor circuit 5 and DSP307 regarding the axial electromagnet 53z. It is a block diagram which shows the modification 1. FIG. It is a block diagram which shows the modification 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic bearing 2 Drive control apparatus 3 Magnetic bearing control part 4 Rotor 5 Sensor circuit 8 Excitation amplifier 9 Display part 51x, 51y, 52x, 52y, 53z Electromagnet 71x, 73 Displacement sensor 301 A / D converter 302,308 D / A converter 306 Storage unit 307 DSP
320 sine wave discrete value generation unit 321 phase shift unit 322 multiplication unit 326 phase adjustment unit

Claims (8)

A carrier wave signal is applied to a sensor that detects the floating position of the supported body, a response wave signal from the sensor is multiplied by a demodulating sine wave signal to perform demodulation, and an electromagnet that supports the supported body in a non-contact manner. In the magnetic bearing control device for controlling the excitation current based on the demodulated signal,
A phase shift unit for shifting the phase of the sine wave signal;
The floating position of the supported body is sequentially set to the first position and the second position, and the phase of the sine wave signal is changed from 0 (deg) to 360 (deg) by the phase shift unit at each setting position. Multiplying signal acquisition means for respectively acquiring the signals after the multiplication at that time;
Phase calculating means for calculating a phase at which the gain of the demodulated signal is maximized based on the signal acquired by the multiplication signal acquiring means;
A magnetic bearing control device comprising: phase setting means for setting the phase calculated by the phase calculating means to a phase shift amount of the phase shift unit in magnetic bearing control. A carrier wave signal is applied to a sensor that detects the floating position of the supported body, a response wave signal from the sensor is multiplied by a demodulating sine wave signal to perform demodulation, and an electromagnet that supports the supported body in a non-contact manner. In the magnetic bearing control device for controlling the excitation current based on the demodulated signal,
A phase shift unit for generating the carrier signal by shifting the phase of the sine wave signal;
The floating position of the supported body is sequentially set to the first position and the second position, and the phase of the sine wave signal is changed from 0 (deg) to 360 (deg) by the phase shift unit at each setting position. Multiplying signal acquisition means for respectively acquiring the signals after the multiplication at that time;
Phase calculating means for calculating a phase at which the gain of the demodulated signal is maximized based on the signal acquired by the multiplication signal acquiring means;
A magnetic bearing control device comprising: phase setting means for setting the phase calculated by the phase calculating means to a phase shift amount of the phase shift unit in magnetic bearing control. In the magnetic bearing control device according to claim 1 or 2,
The phase calculating means calculates, as the phase, a phase at which a difference between a multiplication signal obtained when the first position is set and a multiplication signal obtained when the second position is set is maximized. Magnetic bearing control device characterized by. In the magnetic bearing control device according to any one of claims 1 to 3,
A magnetic bearing control device comprising: A / D conversion means for converting a response wave signal from the sensor into a digital value, and performing demodulation by digital arithmetic processing based on the signal converted into the digital value. In the magnetic bearing control device according to any one of claims 1 to 4,
Each time energization of the magnetic bearing control device is started, a series of operations of obtaining a signal after multiplication by the multiplication signal obtaining unit, calculating a phase by the phase calculating unit, and setting a phase shift amount by the phase setting unit is performed. A magnetic bearing control device. In the magnetic bearing control device according to any one of claims 1 to 5,
A storage unit for storing the phase shift amount set by the phase setting unit;
A magnetic bearing comprising: an abnormality warning unit that issues a bearing abnormality warning when a phase deviation calculated by the phase calculation unit with respect to the phase shift amount stored in the storage unit is greater than or equal to a predetermined reference value. Control device. A carrier wave signal is applied to a sensor that detects the floating position of the supported body, a response wave signal from the sensor is multiplied by a demodulating sine wave signal to perform demodulation, and an electromagnet that supports the supported body in a non-contact manner. In the magnetic bearing control device for controlling the excitation current based on the demodulated signal,
A phase shift unit for shifting the phase of the sine wave signal;
The floating position of the supported body is sequentially set to the first position and the second position, and the phase of the sine wave signal is changed from 0 (deg) to 360 (deg) by the phase shift unit at each setting position. Multiplying signal acquisition means for respectively acquiring the signals after the multiplication at that time;
Phase calculating means for calculating a phase at which the gain of the demodulated signal is maximized based on the signal acquired by the multiplication signal acquiring means;
Determination means for determining whether or not a deviation of a phase calculated by the phase calculation means with respect to a predetermined reference is greater than or equal to a predetermined value each time the magnetic bearing control device is energized;
A magnetic bearing control device comprising: an abnormality warning unit that issues a bearing abnormality warning when the determination unit determines that the value is equal to or greater than a predetermined value. A magnetic bearing control device according to any one of claims 1 to 7,
A magnetic levitation device comprising: a magnetic bearing controlled by the magnetic bearing control device.

Images